Production process and production line for manufacturing articles from hardenable metal materials

ABSTRACT

In a method of manufacturing articles ( 8 ) in hardenable metal materials, a shaped workpiece ( 5.1, 5.2 ) with closed cross-section is hardened. The hardened workpiece ( 5.1, 5.2 ) is separated into at least two parts, where each part constitutes one shaped open cross-section. The invention also concerns a manufacturing process and a production line for the manufacture of articles ( 8 ) in hardenable metal materials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national phase filing under 35 U.S.C. § 371of PCT/SE01/02214 filed Oct. 11, 2001, which PCT application claimsforeign priority from Swedish Patent Application No. 0003781-2 filedOct. 19, 2000.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention concerns a method of manufacturing articles inhardenable metal material. The invention also concerns a manufacturingprocess and a production line.

2. Description of the Background Art

At present, many structural articles are products manufactured in theform of or based on components, details and/or blanks that aremanufactured in material that can be processed and shaped in differentways and thereafter hardened by heating and subsequent quenching. Thematerials used are mainly iron and steel alloy or other metals. If thearticle after shaping has an open cross-section, then the hardeningprocess comprising heating and quenching will exert great strain on thearticle. Stress often arises in the material and gives rise todeformations that are difficult to reduce. At present, the hardenedarticle with open cross-section must often be straightened or reshapedin other suitable ways in order to be utilized. If the tolerances onshape are narrow, this will result in many hardened articles beingdiscarded as seconds or being destroyed.

If the heating takes place in an arrangement containing an inductor andthe articles have an open cross-section then the heat distributionwithin the articles will not be optimum. In turn, this will result in anuneven hardenature distribution in each article, which leads toadditional risks of material strain arising.

SUMMARY OF THE INVENTION

The object of the present invention is to achieve a method ofmanufacturing articles in hardenable material that, amongst otherthings, will solve the aforesaid problems. The method according to thepresent invention comprising the steps of:

-   -   (a) providing a shaped workpiece which closed cross-section;    -   (b) hardening the shaped workpiece to create a hardened        workpiece; and    -   (c) dividing the hardened workpiece into at least two parts,        where each part constitutes one shaped and hardened article with        an open cross-section.

The invention also concerns a manufacturing process and a productionline which implement the method.

Central to the method according to the present invention is to avoidarticles with open cross-sections when hardening. This is possible byproducing and shaping a workpiece with a closed cross-section prior tohardening, hardening the workpiece with the closed cross-section and,subsequent to hardening, dividing the workpiece into parts with opencross-section that have been shaped and hardened. From these parts isobtained the hardened articles of the desired shape. The workpiece withits closed cross-section is relatively stable and its shape does notchange to the same extent as an open profile under hardening. Aworkpiece with closed cross-section also facilitates the distribution ofheat throughout the material during induction heating, which furtherimproves the hardening.

BRIEF DESCRIPTION OF THE DRAWINGS

The method according to the present invention is described below withreferences to some embodiments shown in the attached figures. Articlesand parts with the same denomination and function included in differentobjects have been given the same reference designation but with a suffixto identify the specific object to which they belong.

FIG. 1 illustrates, in a schematic way, a process for manufacturingarticles in hardenable material where the method according to thepresent invention is employed.

FIG. 2 illustrates a perspective view of a shaped sectional element.

FIG. 3 illustrates an end view of two sectional elements that have beenplaced together and joined to form one workpiece for hardening.

FIG. 4 illustrates an end view of another shaped sectional element.

FIG. 5 illustrates an end view of the sectional element of FIG. 4 thathas been folded and joined and thereby forms one workpiece forhardening.

DETAILED DESCRIPTION OF THE INVENTION

The method according to the present invention can be integrated as onepart, or actually as several parts, of a manufacturing process (see FIG.1). Such a manufacturing process may well include a shaping step A, ajoining step B, a hardening step C and a separating step D. Thehardening step C normally includes a heating step C₁ and a cooling stepC₂.

The manufacturing process can be divided into the steps A–D indistinctly individual workstations. Certain steps are so independent ofthe previous and/or the subsequent step that the work being carried outin these steps can be carried out in a different place and at anothertime. All or some of the steps A–D in the manufacturing process incombination can also constitute a more continuous line production.

Each process step requires at least one specific arrangement for thework/processing that is to be carried out at each step. The work beingcarried out in several process steps can be done in the same arrangementif it is possible to coordinate several functions in one arrangement. Itwould be suitable to arrange the process steps in series if productionis to be automated. The arrangements that enable this method in themanufacturing process form a production line.

Production is based on blanks 1 (see FIG. 1) that can be machined,shaped and hardened by heating and quenching, preferably iron and steelalloy or other metals. The blanks 1 are of a size and shape that issuitable for the chosen method of shaping and the associated means forshaping The blanks 1 are in the form of plate or strip.

The first operation for obtaining a workpiece with closed cross-sectionis to shape the blanks 1 in the shaping step A into sectional elements 2(FIG. 2) . If the blanks 1 are in metal plate, they are fed or placedinto the means for shaping. Before shaping A, the plates are of abreadth and length that results in a sectional element 2 with thedetermined and required dimensions after shaping A. If the blanks 1 arein metal strip, they can either be cut into plates before shaping A or acontinuous-feed shaped section of strip can be cut into suitable lengthsafter shaping A. Shaping takes place in a rolling mill. Roll forming canbe complemented or replaced with another method of shaping, such aspressing. The design of the means for shaping is previously known and isnot described here in detail, nor is it shown in detail in the figures.

Each sectional element 2 has three dimensions with a length l, a breadthb and a height h (see FIG. 2). The sectional element 2 is principallycontinuous with a length l that is greater than both the breadth b andthe height h. The ratio of breadth b and height h is optional. Otherratios between the lengths of the sides are possible however.

Each sectional element 2 includes two flanges 3 running lengthwise andforming the outer parts of the sectional element. Each flange 3 isprincipally flat or includes flat areas.

The sectional element 2 also includes a shaped middle section 4 that ismainly U or C-shaped. The middle section 4 has three walls, where twosides 4 a and 4 b are connected to each other with a middle piece 4 c.The middle piece 4 c is corrugated. The other sides 4 a and 4 b can alsobe fluted, folded or have other types of material shaping (not shown infigures). The middle section 4 is joined to a flange 3 on each side.

In the joining step B after shaping A, the two sectional elements 2 and2′ are joined together to form one workpiece 5.1 (see FIG. 3). Thesectional elements 2 and 2′ are placed together in such a way that theflanges 3 on one element are touching the corresponding flanges 3′ onthe second element. The flat area/areas on each flange touch the flatarea/areas on the opposite flange.

The flanges 3 and 3′ are fastened to each other by a means for fasteningpreviously known, such as welding. The flanges are welded as far out asis possible and suitable on the flat areas. The workpiece 5.1 thenobtains stiffening welded joints 6.1 on each outside edge of twoopposing and joined flanges 3 and 3′ lengthwise along the sectionalelement/workpiece. The workpiece 5.1 now has a hollow closedcross-section 7.1 (see FIG. 3).

After the joining step B, the workpiece 5.1 is hardened in the hardeningstep C where it is heated during the heating step C₁ by a means forheating. (The design of the means for heating is previously known and isnot described here in detail, nor is it shown in detail in the figures.)The workpiece 5.1 is heated to a hardening hardenature that is suitablefor the material in question. A suitable hardenature for boron steel,for example, is around 900° C. After heating, the workpiece 5.1 isquenched in a cooling stage C₂. The workpiece 5.1 is then transferredfrom the means for heating to a means for cooling. (The design of themeans for cooling is also previously known and is not described here indetail, nor is it shown in detail in the figures.) Heating and coolingcan take place in a continuous process where the means for heating isconnected to the means for cooling in such a way that the workpiece 5.1is able to pass these two means after each other through a continuousfeed. This can be achieved automatically. The means for heating and themeans for cooling can alternatively be combined in one means to form ameans for hardening where all the steps in the hardening operation C,including the hardening steps C₁, and C₂, take place in one and the samemeans, even without the need to move the workpiece 5.1.

Once the workpiece 5.1 is hardened after heading C₁ and cooling C₂, thewelded joints 6.1 are removed so that the two sectional elements 2 and2′ are separated in the separation step D of the process. The weldedjoints 6.1 can suitably be cut away, which will cause a loss of part ofthe flanges 3 and 3′. The flanges 3 and 3′ must therefore be slightlyoversize after the shaping step A, so that the shaped and hardenedsectional elements 8 (see FIG. 1), constituting the final product, willexhibit the required dimensions. The degree of oversize principallycorresponds to the amount of material that will be cut off the sectionalelements 2 and 2′ during the separation process D. The flanges 3 and 3′on the sectional elements 2 and 2′ when they are only shaped isconsequently wider than they eventually will be in their final shapedand hardened form. The closer to each edge that the welded joint isplaced, the less material loss will arise.

The welded joints 6.1 have assisted in supporting, stiffening, theworkpiece 5.1, and thereby the two sectional elements 2 and 2′, duringhardening C. The shape of sectional elements 2 and 2′ are thereby lessdistorted than they would be if they had passed the hardening processindividually as two sectional elements with open cross-section.

In order to facilitate the joining step B, the sectional elements 2 and2′ can be shaped and fed from two parallel means for shaping so that thesectional elements 2 and 2′ directly after shaping are combined in therequired way with the flanges 3 and 3′ facing each other

It is naturally possible to join more than two sectional elements toobtain a workpiece with a closed cross-section. These shaped sectionalelements and especially the flanges may need to be another shape thanwhen only two sectional elements are joined together. For instance, itmay be necessary to angle the flanges in relation to the sides of themiddle section of each sectional element. The actual sectional elementsmay have another shape than the one described above as long as they havean open cross-section.

Another method is to shape the blanks 1 in the shaping step A to asectional element 2″ with open cross-section including two principally Cor U-shaped parts 9 a and 9 b joined together with a web 10 (see FIG.4). The web includes two parts 10 a and 10 b that form a flange locatedon each side of the longitudinal axis X of the web 10. Along itslongitudinal axis X, the web can have a notch in the material (not shownin the figures). The sectional element 2″ also has flanges 3″ on eachouter long side parallel with the longitudinal axis X of the web.

The sectional element 2″ is bent/folded along the longitudinal axis X sothat the outer flanges 3″ of the sectional element make contact witheach other. At the same time, the two parts 10 a and 10 b that formflanges will also make contact with each other. The two C or U-shapedparts 9 a and 9 b will then be opposite each other, forming one bodywith hollow closed cross-section 7.2 (see FIG. 5).

If the sectional element 2″ is roll formed, this bending can take placeduring the shaping step A. It is also possible to attain this bendingwith another means for shaping, such as pressing. The flanges 3″ arejoined together in the joining step B as previously described to formone workpiece 5.2. This workpiece 5.2 has one welded joint 6.2 along theflanges 3″ on one side and a material fold 11 on the opposite side. Theside of the workpiece with the material fold 11 can be reinforced with awelded joint similar to the one on the flanges 3″. The workpiece 5.2 nowhas a hollow closed cross-section 7.2 (see FIG. 5).

The hardening step C follows, in which the workpiece 5.2 is hardened aspreviously described. This is followed by the separation step D, wherethe welded joint 6.2 and the outermost part of the material fold 11 areremoved. If the material fold 11 is reinforced with a weld, then this isalso removed. Removal can be made by means for cutting, gas-cutting orclipping. The degree of oversize of the flanges 3″ and the parts 12 aand 12 b forming a flange corresponds to the amount of material to beremoved. The flanges 3″ and the web 10 and the parts 12 a and 12 bforming flanges after shaping are consequently wider than they are to bein the final shaped and hardened sectional element 8. Finally, afterseparation, two shaped and hardened sectional elements 8 are obtainedfor subsequent use. It is principally the C or U-shaped parts 9 a and 9b, parts of the web 10 and the flanges 3″ that form the final sectionalelement 8.

Of course, it is possible to shape the sectional element 2″ by othermethods. The sectional element 2″ can include more than two principallyC or U-shaped parts 9, where each parallel shaped part is joined to theadjacent shaped part via a web 10. whereby the number of webs on eachsectional element 2″ is more than one. The flanges 3″ and the web 10 mayrequire another shape and the bend in each web used to form theworkpiece must be less than in the aforesaid case with only onecoincident web. The webs can be pinched together, at least at each placewhere the material is folded, and given a welded joint in order toobtain the stiffening effect required from the welded joint.

All the described flanges 3, 3′ and 3″ can be fitted with shaped partsused to provide an interlocking effect, such as through a snapfastening. The flanges can also be fastened to each other in other ways.

Induction hardening is facilitated if the article being hardened has aclosed cross-section. For induction hardening, the means for heating canbe designed in such a way that the article passes through an inductioncoil. If the sides of the article match the shape of the coil interior,as is the case with the present invention, the heat will be more evenlydistributed, whereby the risk of material stress will be reduced.

The production rate increases as more than one sectional element ishardened at one time in the hardening process. As at least two sectionalelements can be hardened at the same time instead of only one at a time,the production rate can be doubled during the actual hardening. It isalso possible to increase the production rate even further by joiningmore than two sectional elements 2 and 2′ as described above or byshaping the sectional element 2″ in such a way that the hardenedworkpiece 5.2 can be divided into more than two shaped and hardenedsectional elements.

The present invention can be used for the manufacture and production ofbeams, structural girders, such as vehicle members.

This description of the present invention is not to be regarded as alimitation of the invention but only as an example to facilitatecomprehension of the invention. Adaptations of different parts inrelation to other component parts, choice of material, size adjustments,shape adjustments, replacement parts and articles and everything elsethat is evident or presents itself immediately to a skilled person cannaturally be carried out within the scope of the invention.

1. Method of manufacturing articles of hardenable metal materialscomprising the steps of: (a) providing a shaped workpiece with closedcross-section; (b) hardening the shaped workpiece to create a hardenedworkpiece by heating and subsequent quenching; and (c) dividing thehardened workpiece longitudinally into at least two parts, where eachpart constitutes one shaped and hardened article with an opencross-section.
 2. Method according to claim 1, wherein each shaped andhardened article constitutes one sectional element.
 3. Method accordingto claim 1, wherein at least two shaped sectional elements with opencross-section are placed against each other and joined to provide theshaped workpiece with closed cross-section, the hardened workpiece isseparated after hardening so that at least two shaped and hardenedarticles are obtained.
 4. Method according to claim 3, wherein joiningis achieved by welding.
 5. Method according to claim 1, wherein, duringthe providing step, a shaped sectional element with open cross-sectionincluding at least two longitudinally shaped parts interconnected by aweb is folded along a longitudinal axis in the web, the outer sides ofthe sectional element, parallel to the longitudinal axis of the web, arejoined together, whereby the shaped workpiece with closed cross-sectionis obtained and the hardened workpiece is separated after hardening toform at least two shaped and hardened articles with open cross-section.6. Method according to claim 5, wherein joining is achieved by welding.7. Manufacturing process for the manufacture of articles of hardenablemetal materials, comprising the following steps in the order named: (a)hardening a shaped workpiece with closed cross-section by heating andsubsequent quenching; and (b) separating the shaped workpiecelongitudinally into at least two parts, where each part constitutes oneshaped and hardened article with open cross-section.
 8. Manufacturingprocess according to claim 7, further including the step of joiningtogether at least two shaped sectional elements with open cross-sectionsituated opposite each other to obtain the shaped workpiece with closedcross-section.
 9. Manufacturing process according to claim 7, furtherincluding the steps of: (a) providing a shaped sectional element havingan open cross-section and including at least two longitudinal shapedparts interconnected by a web; (b) folding the sectional element along alongitudinal axis in the web so that outer sides of the sectionalelement are parallel with the longitudinal axis of the web; and (c)joining the outer sides to obtain the shaped workpiece with closedcross-section.
 10. Production line for the manufacture of articles ofhardenable metal materials comprising: (a) means for joining shapedsectional elements to obtain a workpiece; (b) means for hardening theworkpiece by heating and subsequent quenching, the means for hardeningfollowing the means for joining; and (c) means for dividing theworkpiece longitudinally into at least two parts, where each partconstitutes one shaped and hardened article with open cross-section, andthe means for dividing being immediately adjacent the means forhardening so that the work performed by the means for hardening and themeans for dividing is carried out sequentially.